The Whomping Willow is a very valuable, very violent species of magical plant. Whomping Willows attack anyone and anything that comes within range of its branches. A deciduous plant, its limbs function as arms and any damage to them must be treated in much the same way.

Known Whomping Willows

The most famous Whomping Willow is the one planted on the grounds of Hogwarts. The Whomping Willow was planted around the year 1971 to disguise the opening of a secret passage leading from the Hogwarts grounds to the Shrieking Shack in the village of Hogsmeade. It had a small knot near the base. When that was pressed, the tree would become immobilised. This allowed Remus Lupin to travel unnoticed to and from the Shrieking Shack, where he was able to undergo his transformation as a werewolf in privacy.

In 1994, Sirius Black, in his animagus form of a large black dog, dragged Ron Weasley into the secret passage beneath the Willow leading to Hogsmeade's Shrieking Shack. They were quickly followed by Harry and Hermione, then later by Lupin and Snape.

In 1998, Harry, Ron, and Hermione sneaked through the passage under the Willow to the Shrieking Shack during the Battle of Hogwarts. There, they witnessed Snape's murder by Lord Voldemort and his serpent, Nagini.